Question

Checking if an item already exists in listbox

Asked by: lolwtf

Hi experts,

I have a form with a textbox and a listbox next to each other.  You can scan a barcode on a badge, and the ID number will show up in the textbox, then put it in the listbox.  The idea is to create a attendance program for employees.  What I want to do is check the listbox to see if a person is checked in or not, and display a message.  I have some code written so far, but I got stuck.  Can you see if I'm on the right track?  

Dim DSScan As New DataSet
 
Try
 
            If txtScan.TextLength = 9 Then
                DBASchool.SelectCommand.CommandText = "SELECT StudentID, FName, LName FROM tblStudent WHERE StudentID = '" + txtScan.Text + "'"
                DBASchool.Fill(DSScan)
                lstAttendance.Items.Add(DSScan.Tables(0).Rows(0).Item("FName").ToString + " " + DSScan.Tables(0).Rows(0).Item("LName").ToString)
                txtScan.Text = ""
                Label3.Visible = False
 
            ElseIf lstAttendance.Items.Contains() = True Then
                MessageBox.Show("Student already checked in", "Info", MessageBoxButtons.OK, MessageBoxIcon.Information)
                txtScan.Text = ""
            End If
 
        Catch ex As Exception
            Label3.Visible = True
            Console.Beep()
 
        End Try

                                  
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Asked On
2009-10-01 at 12:23:51ID24778193
Tags

VB.NET

,

Microsoft

Topics

Microsoft Visual Basic.Net

,

Microsoft Programming

Participating Experts
1
Points
500
Comments
2

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Answers

 

by: daffyduck14milPosted on 2009-10-01 at 12:51:17ID: 25472538

Hi,

The basis of the code is correct, just the place where you check the existance of the item. As observed below in the code, the ElseIf is moved to the inside of the first if statement (that checks input).

Also note that this code does no checking on database validity (ie. null value in a field). All in all, this should work for your case.

Kind regards,
D.

        Dim DSScan As New DataSet
 
        Try
 
            If txtScan.TextLength = 9 Then
                DBASchool.SelectCommand.CommandText = "SELECT StudentID, FName, LName FROM tblStudent WHERE StudentID = '" + txtScan.Text + "'"
                DBASchool.Fill(DSScan)
 
                If lstAttendance.Items.Contains(DSScan.Tables(0).Rows(0).Item("FName").ToString + " " + DSScan.Tables(0).Rows(0).Item("LName").ToString) = True Then
                    MessageBox.Show("Student already checked in", "Info", MessageBoxButtons.OK, MessageBoxIcon.Information)
                    txtScan.Text = ""
                Else
                    lstAttendance.Items.Add(DSScan.Tables(0).Rows(0).Item("FName").ToString + " " + DSScan.Tables(0).Rows(0).Item("LName").ToString)
                    txtScan.Text = ""
                    Label3.Visible = False
 
                End If
            End If
 
        Catch ex As Exception
            Label3.Visible = True
            Console.Beep()
 
        End Try

                                              
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by: lolwtfPosted on 2009-10-01 at 12:56:02ID: 31636087

Thank you!  It was nice to know that I was on the right track!

20120131-EE-VQP-002

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